Help with 20 amp plug and heater.

NEED: Help with portable electric heaters

Advice needed on portable, high efficiency heaters that would plug into a standard 220 air conditioner outlet (20 amp). We live in an older house and afraid to run too many heaters off the 110 outlets, but the 220 outlets are newer wiring… but we’re having a problem finding a heater that uses that type of plug.

So far, everything we have found has 30 amp requirements and need a much larger plug with heavier wiring. Surely there has to be a heater out there that will plug into a standard 20 amp 220v window air conditioner socket.